US1217873A - Electric insulator. - Google Patents

Description

Reference rm STATES PATENT OFFICE.

NORMAN MARSHALL, OF WEST NEWTONgHASSACHUSETTSJ w t I, 2/ 7, 8 7a Specification of Letters Patent Patented Feb. 27, 1917. Application and June so, 1916. 8e rialllo.104,788. 7 3 E To allwhomitmay concern: handled. The dried. tube is then di ed in Be it known that I, NORMAN MARSHALL, linseed oil and permitted to cure or oxiillze a citizen of the United States, residing at m the air from one to four. days, depending Vest Newton, in the county of Middlesex upon the size and thickness ofthe tube, and 60 .5 and State of Massachusetts, have invented then placed in a drying oven heated by certain new and useful Improvements in steam for a shorter time. Them Electric Insulators; and I do hereby de- "dried tube is then bfiked in an oven at a clare the following to be a full, clear, and temperature of from a to 550 F. until i exact description of the invention, such as the tube ceases to give vo a 1 e material 10 will enable others skilled in the art to which or smoke, this generally taking from 5 to 60 1 No Drawing.

it appertains to make and use the same.

This invention relates to electric insulators, and more particularly to insulators for liningmetal'sockets for nitrogen and other incandescent lamps.

Various types of metal lamp sockets used for electric light globes having carbon or tungsten filaments in avacuum, have a paper or vulcanized fiber insulating lining.

A nitrogen lamp, and large sizes of carbon and tungsten filament lamps, should not be used with such a socket, because the heat generated by the lamp when lighted often ecomes great enough to burn or char such lining, so as to cause short circuits in the lighting circuit and many times setting fire to the adjoining structure. For this reason metal lamp sockets for use with nitrogen and other large lamps have been condemned by SOmunicipal building inspectors and fire insurance companies.

The primary object of the present invention is to provide an electric insulator which has adequate heat resisting properties to permit its use in metal lamp sockets for nitrogen and other high temperature lamps without the danger of failure under high temperature.

Another object of the invention is to pro- 40 vide a process of making insulators by which 4 they may be prepared for the various electrical and heat insulating purposes.

With these objects in view the invention minutes according to the thickness and the size of the tubes. In making linings for the well-known type of lamp socket which has a reduced diameter for a portion of its a lining similar in shape to that shown and described in my Patent No. 784,695 dated March 14, 1905. The drawn tube is then baked in an oven at a temperature from 425 to 700 F. until volatilization ceases.

The product thus obtained is a rigid tube or lining havin a brown or black color and ssessing exoe lent heat and electric insuating properties.

The emulsion of sodium silicate and linseed oil is preferably made by mixing one art of sodium silicate with one part of raw inseed oil. These proportions, however are not essential, since 00d results have een obtained with a mixture containing two parts of sodium silicateto one part of linseed oil, and with a mixture containing two parts of linseed oil to one part of sodium silicate. This emulsion undoubtedly contains a certain amount of sodium soaps, due

to the. unstable character of the sodium silicate and the presence of free alkali in the sodium silicate. In place of the sodium silicate any of the soluble silicates such as potassium or the double salt of sodium and consists in the improved'insulator and the potassium, may be employed. While lin- 3 a 45 process of making the same, which are hereseed oil seems to have the better drying inafter described and particularly defined in properties, other oxidizable oils, such as sovthe claims. bean oil and tun -oil may be employed m In the preferred process of making insue p ace of e msee oil. lating tubes or linings for lamp sockets, The finished product is characterized by blanks of a predetermined shape are cut the following chemical and physical properfrom sheet asbestos and saturated with an emulslon of sodium silicate and linseed oil.

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ties: When the asbestos treated with the above emulsions'is'driedin the air, the sodium. silicate becomes partially dehydrated and the linseed oil oxidizes.

siderable pressure upon an arbor or mandrel In baking the 55 and carefully removed and 'ermitted to dr dried product in an oven at a temperature in the air until, it burdens and cani above 400 F., the sodium silicate is dehydrated and the oil is polymerized or resinified. \Vhile the chemical constitution of the baked product is not known, it undoubtedly contains some reaction products such as the sodium salts of acetic and palmitic acids, but since these are covered with the polymerized oil they do not take up moisture or destroy the dielectric properties of the insulator. The dehydrated sodium silicate is distributed throughout the compound and has its well-known fireproofing properties to resist the action of heat in breaking down the structure of the tube. The solid resinified oil has excellent dielectric properties, and since it is formed at a very high temperature, it is a good heat insulator. The asbestos is a good electric insulator and is very resistant to heat. The solidified linseed oil as well as the sodium silicate act as binders in building up and maintaining the structure of the tube and preventing the structure of the asbestos from breaking down under heat. The coating of linseed oil which is placed upon the tube after the emulsion has dried thereon, becomes oxidized and polymerized in the baking operation and gives the finished product a varnished appearance.

The curing operation of the tube is preferably conducted for a long period at moderate temperatures in the air, so that the oil may become well oxidized. However, the curing operation may be accelerated by drying in a steam heated oven in the presence of air, or by drying a shorter time in the air and finishing the drying in the steam heated oven.

Although it is preferred to bake the product between 425 and 500 R, an excellent product may be obtained by temperatures up to 750 F. The greater the degree of temerature used in baking, the darker the tube )QCOIHQS, until it turns black. A tube baked at the higher degrees of temperature is very stiff and brittle, and although it has a greater strength than the tube made at the lower temperature, the flexibility of the tube having the brown color is very advantageous for use in insulating metal lamp sockets.

\Vhile asbestos is preferably used as a carrier, an insulating tube of good quality may be made with a carrier consisting of a cotton fiber paper or a flax paper.- The heat resisting and insulating properties of the hardened linseed oil and dehydrated silicate will protect this type of paper so that it may be safely used for the smaller sizes of nitrogen lamps.

Sodium silicate has well-known fire protecting properties, and if it is desired to increase the heat resisting properties of the composition, the percentage of sodium silicate is increased. The amount of silicate, however, is limited, since it makes the tube brittle. By mixing the linseed oil with the be used.

lVhile the electric insulator has been described as being especially adapted for insulating metallic lamp sockets. it isnot limited to such use but may be used for practically any heat or electric insulating purpose.

The preferred form of the invention having been thus described, what is claimed as new is 1. An insulator comprising a dielectric carrier impregnated with a dehydrated soluble silicate and a polymerized oil.

2.'An insulator comprising a dielectric heat resisting carrier impregnated with a dehydrated soluble silicate and an oxidized vegetable oil.

3. An insulator comprising asbestos impregnated with a dehydrated soluble silicate anld a polymerized and oxidized vegetable o1 4. An insulating lining for lamp sockets comprising a tube of sheet asbestos which is impregnated with decomposition and reaction products of an emulsion of sodium silicate and raw linseed oil, which has been oxidized and baked at a comparatively high temperature, and characterized by its heat resisting and dielectric properties.

5. An insulating lining comprising an asbestos tube which is impregnated with decomposition and reaction products of a mixture of from 30% to linseed oil with from 70% to 30% of a soluble silicate which has been oxidized and baked at a high temperature, and characterized by its heat resisting and dielectric properties, said insulator varying in color from brown to black in accordance with the higher degree of temperature employed in baking, the black material being more brittle than the brown.

6. An insulator comprising a shaped heat resisting carrier impregnated with a dehydrated soluble silicate and polymerized vegetable oil, and coated with an oxidized and resinified vegetable oil.

7. An insulating lining consisting of an asbestos tube having its diameter reduced for a portion of its length, said tube being impregnated with sodium silicate and polymerized linseed oil, and characterized by its brown-black color and rigid structure.

8. The process of making an insulator comprising saturating a heat resisting ,carrier with a soluble silicate and an oxidizable oil, oxidizing and baking the impregnated carrier.

9. The process of making an insulator comprising saturating a sheet of a heat resisting carrier with an emulsion of a soluble silicate and oxidizable vegetable oil, shaping 106. COMPOSITIONS,

the saturated sheet and dlmg it in an oxidizing atmosphere, and ba g the oxidized article at a comparatively high temperature.

10. The process of making an insulator comprising saturating a sheet of asbestos with an emulsion of sodium silicate and linseed oil, shaping the saturated sheet into a lining tube and drying it in the air, and then baking the dried tube to solidify the silicate and oil.

11. The process of making an insulator comprising saturating a sheet of asbestos with an emulsion of a soluble silicate and an oxidizable vegetable oil, shaping the saturated sheet and drying .it in an oxidizing atmosphere, coating the dried article with an oxidizable oil and curing it in an oxidizable atmosphere, and then baking the coated article at a comparatively high temperature.

COATING oa PLAsup. Cross Reference 12. The process of making an insulator comprisin saturating sheet asbestos in a mixture 0 from 30% to 70% of sodium silicate with from 70% to 30% linseed oil, shaping the saturated sheet and drying it in the air, coating the shaped article with the linseed oil, drying the coated article in the air, and baking the dry-coated article at a temperature of from 400 to 650 F.

13. The process of making a lining for NORMAN MARSHALL.

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